Jun Inui

Bio: Jun Inui is an academic researcher from University of Tokyo. The author has contributed to research in topics: Alkyl & Trifluoromethyl. The author has an hindex of 11, co-authored 25 publications receiving 3255 citations.

Calcium sensitization of smooth muscle mediated by a Rho-associated protein kinase in hypertension

Abstract: Abnormal smooth-muscle contractility may be a major cause of disease states such as hypertension, and a smooth-muscle relaxant that modulates this process would be useful therapeutically. Smooth-muscle contraction is regulated by the cytosolic Ca2+ concentration and by the Ca2+ sensitivity of myofilaments: the former activates myosin light-chain kinase and the latter is achieved partly by inhibition of myosin phosphatase. The small GTPase Rho and its target, Rho-associated kinase, participate in this latter mechanism in vitro, but their participation has not been demonstrated in intact muscles. Here we show that a pyridine derivative, Y-27632, selectively inhibits smooth-muscle contraction by inhibiting Ca2+ sensitization. We identified the Y-27632 target as a Rho-associated protein kinase, p160ROCK. Y-27632 consistently suppresses Rho-induced, p160ROCK-mediated formation of stress fibres in cultured cells and dramatically corrects hypertension in several hypertensive rat models. Our findings indicate that p160ROCK-mediated Ca2+ sensitization is involved in the pathophysiology of hypertension and suggest that compounds that inhibit this process might be useful therapeutically.

The possible role of endothelin-1 in the pathogenesis of coronary vasospasm.

Abstract: We investigated the in vivo vasoconstrictor effects of endothelin-1 (ET-1) on canine coronary arteries and the regulation of ET-1 gene expression with special reference to the pathogenesis of coronary vasospasm. ET-1, administered into the coronary arteries of anesthetized dogs, produced a profound and long-lasting reduction in coronary blood flow with myocardial ischemia. Coronary angiography revealed delayed filling of the distal branches and, in some cases, total occlusion in the epicardial portions of coronary arteries. The coronary vasoconstriction induced by ET-1 subsided after intracoronary administration of nitroglycerin. Pretreatment with the Ca2+-channel antagonist, nitrendipine, suppressed ET-1-induced vasoconstriction. In cultured porcine aortic endothelial cells, ET-1 gene expression was induced by agents related to thrombus formation, such as thrombin and transforming growth factor beta (TGF beta). These findings suggest that ET-1, produced by vascular endothelial cells, may contribute to the regulation of coronary circulation and the pathogenesis of coronary vasospasm with respect to intimal injury and subsequent thrombus formation.

Trans-4-amino(alkyl)-1-pyridylcarbamoylcyclohexane compounds and pharmaceutical use thereof

Abstract: A trans-4-amino(alkyl)-1-pyridylcarbamoylcyclohexane compound of the formula: ##STR1## wherein R 1 and R 2 are the same or different, and respectively represent hydrogen, C 1-10 alkyl, C 2-5 alkanoyl, formyl, C 1-4 alkoxy-carbonyl, amidino, C 3-7 cycloalkyl, C 3-7 cycloalkylcarbonyl, phenyl, phenylalkyl, benzoyl, naphthoyl, phenylalkoxycarbonyl, benzylidene, pyridylcarbonyl, piperidyl, pyrrolidylidene or piperidylidene which may be optionally substituted on the ring or R 1 and R 2 together with the adjacent nitrogen atom form 5 to 6-membered cycle which may have oxygen atom, sulfur atom or optionally substituted nitrogen atom in the cycle, or together with the adjacent nitrogen atom form phthalimido, R 3 represents hydrogen or C 1-4 alkyl, R 4 represents hydrogen or C 1-4 alkyl, R 5 represents hydrogen, hydroxy, C 1-4 alkyl or phenylalkoxy. R 6 represents hydrogen or C 1-4 alkyl, A represents single bond, C 1-5 straight chain alkylene, or alkylene which is substituted by C 1-4 alkyl, n represents 0 to 1, an optical isomer thereof and a pharmaceutically acceptable acid addition salt thereof. These compounds possess antihypertensive activity, and coronary, cerebral and kidney circulation-improving activities and are useful as antihypertensive agents and agents for prevention and treatment of circulatory diseases.

Rho GTPases in cell biology.

Abstract: Rho GTPases are molecular switches that control a wide variety of signal transduction pathways in all eukaryotic cells. They are known principally for their pivotal role in regulating the actin cytoskeleton, but their ability to influence cell polarity, microtubule dynamics, membrane transport pathways and transcription factor activity is probably just as significant. Underlying this biological complexity is a simple biochemical idea, namely that by switching on a single GTPase, several distinct signalling pathways can be coordinately activated. With spatial and temporal activation of multiple switches factored in, it is not surprising to find Rho GTPases having such a prominent role in eukaryotic cell biology.

Specificity and mechanism of action of some commonly used protein kinase inhibitors

Abstract: The specificities of 28 commercially available compounds reported to be relatively selective inhibitors of particular serine/threonine-specific protein kinases have been examined against a large panel of protein kinases. The compounds KT 5720, Rottlerin and quercetin were found to inhibit many protein kinases, sometimes much more potently than their presumed targets, and conclusions drawn from their use in cell-based experiments are likely to be erroneous. Ro 318220 and related bisindoylmaleimides, as well as H89, HA1077 and Y 27632, were more selective inhibitors, but still inhibited two or more protein kinases with similar potency. LY 294002 was found to inhibit casein kinase-2 with similar potency to phosphoinositide (phosphatidylinositol) 3-kinase. The compounds with the most impressive selectivity profiles were KN62, PD 98059, U0126, PD 184352, rapamycin, wortmannin, SB 203580 and SB 202190. U0126 and PD 184352, like PD 98059, were found to block the mitogen-activated protein kinase (MAPK) cascade in cell-based assays by preventing the activation of MAPK kinase (MKK1), and not by inhibiting MKK1 activity directly. Apart from rapamycin and PD 184352, even the most selective inhibitors affected at least one additional protein kinase. Our results demonstrate that the specificities of protein kinase inhibitors cannot be assessed simply by studying their effect on kinases that are closely related in primary structure. We propose guidelines for the use of protein kinase inhibitors in cell-based assays.

Calcium sensitization of smooth muscle mediated by a Rho-associated protein kinase in hypertension

Abstract: Abnormal smooth-muscle contractility may be a major cause of disease states such as hypertension, and a smooth-muscle relaxant that modulates this process would be useful therapeutically. Smooth-muscle contraction is regulated by the cytosolic Ca2+ concentration and by the Ca2+ sensitivity of myofilaments: the former activates myosin light-chain kinase and the latter is achieved partly by inhibition of myosin phosphatase. The small GTPase Rho and its target, Rho-associated kinase, participate in this latter mechanism in vitro, but their participation has not been demonstrated in intact muscles. Here we show that a pyridine derivative, Y-27632, selectively inhibits smooth-muscle contraction by inhibiting Ca2+ sensitization. We identified the Y-27632 target as a Rho-associated protein kinase, p160ROCK. Y-27632 consistently suppresses Rho-induced, p160ROCK-mediated formation of stress fibres in cultured cells and dramatically corrects hypertension in several hypertensive rat models. Our findings indicate that p160ROCK-mediated Ca2+ sensitization is involved in the pathophysiology of hypertension and suggest that compounds that inhibit this process might be useful therapeutically.

The selectivity of protein kinase inhibitors: a further update.

Abstract: The specificities of 65 compounds reported to be relatively specific inhibitors of protein kinases have been profiled against a panel of 70-80 protein kinases. On the basis of this information, the effects of compounds that we have studied in cells and other data in the literature, we recommend the use of the following small-molecule inhibitors: SB 203580/SB202190 and BIRB 0796 to be used in parallel to assess the physiological roles of p38 MAPK (mitogen-activated protein kinase) isoforms, PI-103 and wortmannin to be used in parallel to inhibit phosphatidylinositol (phosphoinositide) 3-kinases, PP1 or PP2 to be used in parallel with Src-I1 (Src inhibitor-1) to inhibit Src family members; PD 184352 or PD 0325901 to inhibit MKK1 (MAPK kinase-1) or MKK1 plus MKK5, Akt-I-1/2 to inhibit the activation of PKB (protein kinase B/Akt), rapamycin to inhibit TORC1 [mTOR (mammalian target of rapamycin)-raptor (regulatory associated protein of mTOR) complex], CT 99021 to inhibit GSK3 (glycogen synthase kinase 3), BI-D1870 and SL0101 or FMK (fluoromethylketone) to be used in parallel to inhibit RSK (ribosomal S6 kinase), D4476 to inhibit CK1 (casein kinase 1), VX680 to inhibit Aurora kinases, and roscovitine as a pan-CDK (cyclin-dependent kinase) inhibitor. We have also identified harmine as a potent and specific inhibitor of DYRK1A (dual-specificity tyrosine-phosphorylated and -regulated kinase 1A) in vitro. The results have further emphasized the need for considerable caution in using small-molecule inhibitors of protein kinases to assess the physiological roles of these enzymes. Despite being used widely, many of the compounds that we analysed were too non-specific for useful conclusions to be made, other than to exclude the involvement of particular protein kinases in cellular processes.

Protein kinases--the major drug targets of the twenty-first century?

Abstract: Protein phosphorylation regulates most aspects of cell life, whereas abnormal phosphorylation is a cause or consequence of disease. A growing interest in developing orally active protein-kinase inhibitors has recently culminated in the approval of the first of these drugs for clinical use. Protein kinases have now become the second most important group of drug targets, after G-protein-coupled receptors. Here, I give a personal view of some of the most important advances that have shaped this field.